Optical waveguides and resonators embedded within a photonic crystal are potentially vital components for optical signal processing While three-dimensional (3D) photonic crystals (PhCs) can, in principle, eliminate the radiative losses that beset 2D devices, most 3D fabrication techniques are not sufficiently flexible to allow facile introduction of the structural 'defects' needed to define functional devices -3 In opal-like PhCs, defects can be made by surface modification4-6 and overgrowth6, or by multi-photon polymerization of infiltrated resin However inverse opal PhCs have small photonic bandgaps and significant spontaneous defect densities. Electron- beam lithography builds structures layer by layer, so that defects can be arbitrarily located, but the overall PhC thickness is limited by long processing cycles and the build up of thermal stresses.
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